Lactic acid bacteria are a generic term for microorganisms which commonly produce lactic acid by fermentation, and they play an important role in improving the flavor, texture, and nutritional value of a food product, imparting a preservative quality to a food product, and so on. Moreover, various physiological effects of lactic acid bacteria such as intestinal flora-improving effects and intestinal function-regulating actions brought about by ingestion of live lactic acid bacteria have been revealed, and research and development of food products, health-promoting food products, pharmaceutical products, and the like utilizing these physiological actions exerted by lactic acid bacteria have been conducted.
Further, plant-derived lactic acid bacteria, which play a major role in traditional fermented food products such as miso (fermented soybean paste) and Japanese pickles, are considered to be strong lactic acid bacteria which can survive in a condition of poor nutrient balance, and are rapidly gaining attention. However, compared to animal-derived lactic acid bacteria, plant-derived lactic acid bacteria have particularly low proliferation ability in milk, which has limited the utilization of plant-derived lactic acid bacteria in milk products.
Thus, if the promoted proliferation of plant-derived lactic acid bacteria, increased bacterial concentration, reduced fermentation time, and the like, can be successfully achieved in lactic acid fermentation in which plant-derived lactic acid bacteria is employed, then it will bring tremendous industrial utility value.
So far, it has been reported that sake lees and sake lees extracts or enzymatic degradation products of sake lees (refer to Patent documents 1 to 3), distillation residue liquids of shochu made from barley (Shochu is Japanese distilled spirit) (refer to Patent Document 4), wort fermentation products (refer to Patent Document 5), malted soybean fermentation products (refer to Patent Document 6), and the like have proliferation promoting actions on lactic acid bacteria.
However, it has not been revealed what kind of components of sake lees and distillation residue liquids of shochu can exhibit proliferation promoting actions on lactic acid bacteria. There is also a problem that sake lees impairs the flavor, appearance, and color tone of a fermented food product, which is the end product, due to its peculiar smell and color.
Meanwhile, malted rice, which is obtained by allowing koji mold (certain Aspergillus species) to grow on rice, is known to have a hypotensive action (refer to Patent Document 7), while water extracts of malted rice are known to have a moisturizing action (refer to Patent Document 8).
However, it has not been known that water extracts of malted rice exhibit proliferation promoting actions on plant-derived lactic acid bacteria and antibacterial activity against bacteria other than lactic acid bacteria.